A difficult obstacle associated with the exploration and production of oil and gas is management of significant ocean currents. These currents can produce vortex-induced vibration (VIV) and/or large deflections of tubulars associated with drilling and production. VIV can cause substantial fatigue damage to the tubular or cause suspension of drilling due to increased deflections. Both helical strakes and fairings can provide sufficient VIV suppression.
Buoyancy cans are used for a variety of applications in the ocean. Their primary function is to support something that is heavier than water to keep it from sinking. Popular uses include their use for providing temporary or permanent support for tubulars such as risers and tendons.
Buoyancy cans may be cylindrical, much like a tubular, and therefore similar to a tubular, also experience VIV. However, due to the potentially large diameter of buoyancy cans, conventional helical strakes with an underlying shell cannot easily be fabricated for large diameters. In addition, helical strakes are usually banded to the underlying tubular and their ability to provide a sufficient clamping force is inhibited with the increased friction associated with larger diameters.
While fairings may also be used for suppressing VIV of buoyancy cans, the size required for a buoyancy can fairing is also problematic. In addition, since fairings weathervane with changes in current direction, they must be kept relatively free of marine growth, which may be expensive for large diameter structures.